DESC:TECHNICAL FIELD
[001] The embodiments herein generally relate to a connecting rod for an automotive engine, more particularly but not exclusively to a split connecting rod in which a parting line or separation between a shank and a cap extends obliquely to a central line defined by the shank to ensure less trajectory of articulation (connecting rod sweep) and having form threads to fasten the cap to the shank.
BACKGROUND
[002] Connecting rod is one of the primary components in an IC engine. The main function of the connecting rod is to connect piston to a crankshaft, and to convert reciprocating motion into rotating motion. The connecting rod includes a shank, a small end and a big end opposite to the small end. The small end of the connecting rod connects to the piston with a piston pin and the big end connects to the crankpin through a connecting rod cap with two bolts. It acts as rigid lever helping convert combustion energy to rotational energy.
[003] The conventional straight connecting rod design is suitable for small engine designs which are with lower connecting rod big end diameters. In straight connecting rod the split line for cap is normal to the connecting rod vertical axis (line joining small end center and big end center). For large commercial high-performance diesel applications which are with higher peak firing pressure, connecting rod with bigger bearing diameters are required which need the connecting rod with cap inclined design.
[004] In two-part connecting rods, especially those in which the parting plane or separation between the cap and the shank extends obliquely to the length of the shank, the rod is placed under load during the operation of the engine or machine. Complicated stress patterns are developed in the fastening screws which make the design and dimensioning difficult. The cap itself is deformed in a manner during operation. In the connecting rods of this type the screws bear against the cap at the heads thereof or by means of nuts threaded onto them and are held substantially stationary with respect to the cap at their points of engagement with the cap. Consequently, the deformations of the cap impose on the screws transverse stresses additional to their tensile stresses, and these transverse stresses substantially increase the total stress or load to which the material of the screws is subjected, and can under certain circumstances give rise to malfunction or trouble.
[005] In conventional connecting rod the threading of big end bolt comes closer to the load path of the combustion force. Threads become the load bearing members and are subjected to bending loads. There are high chances of the fatigue failure from this location. In addition to combustion loads, the threads are subjected to assembly loads and inertia load due to reciprocating loads on connecting rod. Last unengaged threads have multi-axial loading from bolt pretention, bearing shell interference, inertia forces and combustion forces. There are high chances of the fatigue failure from bolt thread location.
[006] Therefore, there exists a need for a split connecting rod in which a parting line or separation between a shank and a cap extends obliquely to a central line defined by the shank to ensure less trajectory of articulation (connecting rod sweep) and having form threads to increase fatigue safety factor. Further, there exists a need for a split angle connecting rod which obviates the aforementioned drawbacks.

OBJECTS
[007] The principal object of the embodiments disclosed herein is to provide a split connecting rod in which a parting line or separation between a shank and a cap extends obliquely to a central line defined by the shank.
[008] Another object of the embodiments disclosed herein is to provide a split connecting rod having an optimized design with a predetermined inclination angle between the shank and the cap.
[009] Yet another object of the embodiments disclosed herein is to provide a split angle connecting rod having form threads to increase fatigue safety factor.
[0010] Still another object of the embodiments disclosed herein is to provide a split connecting rod having a V shaped merging at the shank to move away the merging end from threaded openings.
[0011] Another object of the embodiments disclosed herein is to provide a split connecting rod having an optimized bolt center distance to maintain the threaded openings away from a load line.
[0012] Also another object of the embodiments disclosed herein is to reduce number of assembly operations and improve assembly line operational time.
[0013] Another object of the embodiments disclosed herein is to design a compact split connecting rod for commercial engine with higher PFP.
[0014] Still another object of the embodiments disclosed herein is to reduce the overall cost of the engine, process and setup achieving basic motive in an efficient way with highest reliability.
[0015] These and other objects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF DRAWINGS
[0016] The embodiments of the invention are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0017] FIGS. 1 and 2 depict a perspective view and a sectional view of a conventional connecting rod, according to an embodiment of the invention as disclosed herein;
[0018] FIG. 3 depicts a perspective view of a split connecting rod, according to an embodiment of the invention as disclosed herein;
[0019] FIG. 4 depicts a sectional view of a split connecting rod, according to an embodiment of the invention as disclosed herein; and
[0020] FIG. 5 depicts an enlarged sectional view of a split connecting rod at first end, according to an embodiment of the invention as disclosed herein.

DETAILED DESCRIPTION
[0021] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0022] The embodiments herein achieve a split connecting rod in which a parting line or separation between a shank and a cap extends obliquely to a central line of shank. Referring now to the drawings, and more particularly to FIGS. 1 through 5, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0023] FIGS. 1 and 2 depict a perspective view and a sectional view of a conventional connecting rod, according to an embodiment of the invention as disclosed herein. In the conventional connecting rod the split between the shank and the cap is provided perpendicular to the length of the shank. The conventional straight connecting rod design is suitable for small engine designs which are with lower connecting rod big end diameters. In straight connecting rod the split line for the cap is normal to the connecting rod vertical axis (line joining small end center and big end center).
[0024] FIG. 3 depicts a perspective view of a split connecting rod, according to an embodiment of the invention as disclosed herein. The embodiments herein relates to a split connecting rod 100 (also referred as connecting rod 100 in this description) of a heavy-duty diesel engine which has inclined split design and form threads. In an embodiment, the split connecting rod includes a shank 102 having a first end 104 (also referred as big end in this description) and a second end 106 (also referred as small end in this description), a cap 108, an inclined predetermined angle a, a central line L of said shank 102, at least two first threaded openings (not shown), at least one threaded fastener 110, at least two second threaded openings (not shown).
[0025] The embodiments herein provide an optimized design for the split connecting rod 100 for a compact cylinder block of internal combustion engine by having higher cap inclination angle a while keeping threaded fasteners 110 away from the central line L, optimization of the design at merging 112 of connecting rod shank and first end (big end) and introduction of form threads to increased fatigue factor of safety of the connecting rod 100.
[0026] FIG. 4 depicts sectional view of a split connecting rod, according to an embodiment of the invention as disclosed herein. The connecting rod 100 includes the shank 102. The shank 102 includes the first end (big end) 104 and the second end (small end) 106. The second end 106 is opposite to the first end 104. The connecting rod 100 further includes the cap 108. The cap 108 is adapted to be coupled to the shank 102 at the first end 104. Further, the shank 102 and the cap 108 includes mating surfaces which are inclined to a predetermined angle “a” with respect to the central line L of the shank 102. In an embodiment, the central line L is also referred as a line of gas load L. The shank 102 and the cap 108 are split at the angle a which is inclined to the line of gas load L. The predetermined inclined angle a ranges between 40? to 60?. For example, the connecting rod 100 is designed at a split angle of 42 ? to ensure less trajectory of articulation (connecting rod sweep). However, it is also within the scope of the invention to provide the inclined angle a in any predetermined angle ranging from 20? to 90? without otherwise deterring the intended function of inclination to mating surfaces as can be deduced from the description and corresponding drawings.
[0027] The cap 108 includes at least two first threaded openings (not shown). Each of the first threaded openings (not shown) is adapted to receive at least one threaded fastener 110. Further, the at least two first threaded openings in the cap 108 are produced by form threading. Further, the shank 102 includes the atleast two second threaded openings (not shown). The at least two second threaded openings are provided at the first end (big end) 104. Each of the second threaded openings is adapted to receive the threaded fastener 110 that engages and clamps the cap 108 to the shank 102. The second threaded opening includes a front end (not shown) which is integrated to the cap 108, and a rare end which is disposed towards a merging 112 of the shank 102 and the first end 104. The first threaded openings and the second threaded openings are integrated or aligned with each other such that there central axis (not shown) lie in the same line. Further, the integration of the first threaded openings with the second threaded openings may include a tap depth and a drill depth ranging from 50mm to 55mm and 55mm to 65mm respectively. Further, a big end bore and a tap hole may range between 2mm to 5mm. The cap 108 engages with the shank 102 to define a crankshaft bore B. The diameter of the crankshaft bore B may vary from 65mm to 75mm. For example the bore diameter may be 69mm. The at least two threaded fasteners 110 are bolts. However, it is also within the scope of the invention to provide any type of connecting member between the cap 108 and the shank 102 without otherwise deterring the intended function of connecting as can be deduced from the description and corresponding drawings. The at least two threaded fasteners 110 are disposed parallel to each other and perpendicular to the mating surfaces or inclined split line S of the shank 102 and the cap 108.
[0028] FIG. 5 depicts an enlarged sectional view of a split connecting rod at first end, according to an embodiment of the invention as disclosed herein. Furthermore, the connecting rod 100 includes a ‘V’ shaped merging 112 at an interface of the shank 102 and the big end 104. The interface is introduced in the design of the connecting rod to maximize the material availability and strength during load transfer from the small end 106 to the big end 104. The V shaped shank with a flatter tip merging 112 at big end interface instead of a regular U shaped shank tip helps in keeping groove notch away from the threaded openings ensuring enough wall thickness. Further, the connecting rod 100 includes a predetermined bolt distance D defined between the shank 102 and the second threaded openings to move the second threaded openings away from the load line defined along the shank 102. The distance between the V shaped merging 112 and the rear end of the second threaded opening may range from 8mm to 10mm. For example the distance may be 8.293. The bolt center distance d of the connecting rod may range between 80mm to 85mm. The Shifting the second threaded opening away from load line results in lower stresses at threading area which helps in improving the fatigue factor of safety. Further, the threaded fasteners 110 are moved down towards the split line S to take threads away from the load path which resulted in lesser stresses on last engaged thread.
[0029] Further, the threads in the first threaded openings and the second threaded openings are produced by form threading instead of thread cutting. Thereby, the sharp corners in the threading are avoided which are the main source for the stress concentration and act as source for the crack generation. Due to optimization of the connecting rod 100 design along with the change of threading type fatigue factor of safety is improved in simulation which is also confirmed with the fatigue testing of the connecting rod.
[0030] Simulations like FEA analysis are performed to estimate the fatigue factor of safety on the connecting rod and particularly in the threaded fastener zone. Further, fatigue test is performed to physically verify the fatigue factor of safety and connecting rod durability under actual conditions. This results in the optimal design ensuring sufficient structural strength and rigidity. The embodiments herein could be further used in similar compact applications for other connecting rod designs.
[0031] The technical advantages provided by the embodiments herein include, ensuring a lower connecting rod sweep and a compact cylinder block resulting in lower weight, decreased stress concentration at the bolt threads from the line of combustion loads, improves stiffness, rigidity & reliability of the connecting rod by achieving the desired fatigue factor of safety.
[0032] The internal combustion engine is configured with inclined split connecting rod with introduction of form threads. The flatten ‘V’ merging 112 between the shank 102 and big end 104 is introduced in the design to increase the center distance between the fasteners 110 and the shank 102. Further, the connecting rod 100 includes, form threads in place of the cut threads to decrease stress concentration and improved the fatigue factor of safety.
[0033] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
,CLAIMS:We claim,
1. A split connecting rod 100, comprising:
a shank 102 having a first end 104 and a second end 106 opposite to said first end 104; and
a cap 108 adapted to be coupled to said shank 102 at first end 104,
wherein
said shank 102 and said cap 108 includes mating surfaces which is inclined to a predetermined angle a with respect to a central line L of said shank 102;
said cap 108 includes at least two first threaded openings, said first threaded opening adapted to receive at least one threaded fastener 110;
said shank 102 includes at least two second threaded openings at first end 104, said threaded opening adapted to receive said threaded fasteners 110 that engages and clamps said cap 108 to said shank 102.
2. The split connecting rod 100 as claimed in claim 1, wherein the mating surfaces of said shank 102 and said cap 108 are inclined at an angle a which ranges from 40 ° to 60 ° to said central line L of said shank 102.
3. The split connecting rod 100 as claimed in claim 1, wherein said cap 108 engages with said shank 102 to define a crankshaft bore.
4. The split connecting rod 100 as claimed in claim 1, wherein said at least two first threaded openings in cap 108 and at least two second threaded openings in shank 102 are produced by thread forming process.
5. The split connecting rod 100 as claimed in claim 1, wherein the at least two threaded fasteners 110 are bolts.
6. The split connecting rod 100 as claimed in claim 1, wherein the at least two threaded fasteners 110 are disposed parallel to each other and perpendicular to said mating surfaces of said shank 102 and said cap 108.
7. The split connecting rod 100 as claimed in claim 1, wherein said connecting rod 100 includes a predetermined bolt distance D defined between said shank 102 and said second threaded openings to move said second threaded openings away from a load line defined along said shank 102.
8. The split connecting rod 100 as claimed in claim 1, wherein said connecting rod 100 includes a V shaped merging 112 at interface of said shank 102 and said first end 104.